Pneumatically operated welder head construction



Dec. 8, 1953 F. F. FOLMER PNEUMATICALLY OPERATED WELDER HEAD CONSTRUCTION Filed Dec.

IN VEN TOR.

1994/36? FAIAR /C K F04 Mi MN 3 .wv vwvv R m Patented Dec. 8, 1953 UNITED STATES PATENT OFFICE PNEUMATICALLY OPERATED WELDER HEAD CONSTRUCTION 3 Claims.

This invention relates to a welding gun and more particularly to a pneumatically operated head for a welding gun which supports and actuates the welding electrode.

It is an object of this invention to produce a head for a welding gun which is of simple construction, which operates very efficiently, and in which the operative parts are effectively protected from weld spatter.

In the drawing:

Fig. l is a view showing a welder head assembly of this invention with the electrode secured thereto.

Fig. 2 is a longitudinal sectional view of the welder head.

Fig. 3 is a sectional view taken substantially along the lines 3-3 in Fig. 2.

Fig. 4 is a View of the welder head shown in Fig. 2 looking from the electrode end.

Referring to the drawing, the head comprises a body it in the form of a cylinder closed at one end by a fitting I l which is provided with threads at 2 for threaded engagement with a holder (not shown). The fitting ii may be secured to cylinder It as by welding at 9. Within cylinder it there are arranged two pistons 13 and I4. Piston it has formed integrally therewith a piston rod is having a reduced threaded end portion it which supports piston i3. Piston I3 is secured at the inner end of rod it by a nut I! and a lock washer iii. The arrangement is such that pistons it and i are fixedly connected together in spaced relation for movement in unison.

Cylinder It is provided with an enlarged bore 53 at one end which terminates in a shoulder Within the enlarged bore i9 there is arranged a sleeve member which has a body portion 22 abutting against the shoulder 20 and an axially extending tubular portion 25. Body portion 22 has a central, axially extending bore which slidably supports piston rod It so that the piston E3 is movable in the bore 25 of cylinder ill and the piston I4 is movable in the bore 26 of sleeve member 2!. The sleeve member 2! is retained in position abutting against shoulder by a bushing 2? at the other end of cylinder Bushing 27 is secured to cylinder it by suitable means, such as pins 28.

In addition to the piston rod I5, piston I l has formed integrally therewith and on the face opposite rod It an extension 30. Extension 30 is formed with flat side faces as at 3| and bushing 2'5 is provided with a non-circular opening 32 which conforms in shape to the cross section of extension 39. At its extreme outer end, extension 39 is provided with a tapered shank 33 on which may be secured an electrode 3 1 as by means of a set screw 35.

Fitting II is fashioned with an axial inlet passage 3t which is enlarged as at 37 to accommodate the nut IT at the inner end it of piston rod l5. Inlet passage 3% is threaded as at 38 for connection with a suitable conduit leading from a source of air under pressure. The welding head is preferably provided with a second inlet opening 39 which is radially disposed and which communicates with the enlargement 31!. The body portion 22 of sleeve 2i is also provided with an inlet port it which is connected with an axially extending passage l! which communicates with the chamber defined by piston 13 and body portion 22. Cylinder it is apertured as at 22 to permit a second air-supply conduit to be threadedly engaged in the port it. Piston rod is is formed with an axial passage 43. Passage :33 is open at the end of the rod 15 which supports piston l3 so as to communicate with inlet passage 35 and port 35. At its inner end passage 13 intersects with a radial passage 44. Passage it is spaced axially inwardly of piston is and is disposed such that with the pistons in the retracted position, such as illustrated by solid lines in Fig. 2, the outer end of passage it is closed by the body portion 22 of sleeve 2|.

Each of the pistons is provided with a circumferential groove 45 on the cylindrical surface thereof in which is seated an annular rubber seal 45. Sleeve 2! is sealed with respect to the bore is of cylinder It by an annular rubber seal M which is seated in a circumferential groove 38 around the outer surface of body 22. he body 22 is also sealed with respect to the rod it by an annular rubber seal is which is seated within a groove 5%? formed in the bore To assemble the head, the rod it is first fitted through the bore 2 3 in the body portion .22 of sleeve 2! so that the piston It is disposed within the bore 2t of sleeve 2i. Piston It is then se-= cured to the end of rod It as by the nut ii and lock washer E8. The entire assembly is then slipped into the cylinder [0 with the sleeve 2i engaging the bore 9. The sleeve is adjusted such that the port 40 is aligned with the opening 52 in the cylinder it. Thereafter, the bushing 72"! is slipped over the end of extension so as to abut against the end of the tubular portion 23 of sleeve 2| and the entire assembly is locked in place by pins 28.

In operation an air-inlet line may be connected either with port 355 or with port depending on 55 the type of gun on which the head is used. if the inlet line is connected with port then port 38 would be provided with a suitable plug. A second air-inlet line is connected. with port 40. The air-supply lines leading to port 38 or 559, as the case may be, and port 40 are connected through a valve (not shown) which may be con trolled by the trigger of the gun or by sequence controls of the welding: machine for admitting air under pressure to one side of piston [3 on the work stroke through port 38 or Eat and to the other side of piston IS on the return stroke through port id. In the position indicated by full lines in Fig. 2, pistons l3 and i i are in the retracted position. Air is directed through either port 38 or 39 into the enlargement 37 and into the axial passage it in rod 45. The pressure of the air admitted to enlargement it causes pistons l3 and i l to move outwardly or to the right.

At the start of the outward movement of the pistons, the pressure acts against that face of piston 13 which is disposed toward the enlargement 31. As soon as the pistons have moved outwardly or to the right a distance such that the radial clears the end race of body 22, air is directed through passage lit and passage M to the space between body 22 and piston l4. Assuming that the air is supplied from a source or constant pressure, the total efiective pressure with which the pistons are moved outwardly is substan ially increased. as soon as the radial passage M moves outwardly beyond the edge of body 22. Pistons l3 Hi may llOVG outwardly to extreme position shown clotted lines Fig. 2 wherein piston lt abuts against sleeve 2! and piston It abuts against bushing 27. When the trigger on the welding gun is released or actuated to reverse the application of pressure, the supply of air to port St or 39 is discontinued and the air is directed through port and axial passage A l to the opposite face of piston 13. This causes the pistons to move inwardly Or towards the left. As piston l3 moves towards the left, the air in the chamber between piston l3 and fitting It is exhausted through port 33 or lit and the air between piston M and body portion 22 of sleeve 2! is exhausted through radial passage 44, axial passage to ports 33 or However, after the pistons have moved inwardly an extent such that the radial passage is closed by the body portion 22 of sleeve iii, the air between piston 14 and body portion 22 is trapped. This trapped air provides cushion on the return stroke which prevents a full impact or the pistons against their associated stops, that is, fitting l l and body portion 22. The air trapped between piston l4 and body 22 seeps around the rod 15 back into radial passage it and axial passage ii so that the pistons return smoothly to their extreme inward position shown by full-lines in 2.

It will be noted that on the work stroke the total effective piston area generally includes the face area of piston it and the area oi: piston I4 less the cross sectional area of piston rod Ill. Thus the total effective piston area on the work stroke is substantially greater than the total cross sectional area of the cylinder. It will also be noted that the total volume of air required to return the pistons to their innermost posi tion after a full work stroke is less than half the volume of air required for a lull work stroke. This multiple piston arrangement is therefore conducive to efficient operation and makes for compactness in size.

The compactness in size is especially desirable in welding machines for producing a series or relatively closely spaced spot welds. A standard spacing of welds for a close spot-weld pattern is generally about two inches. I have found that with the welding head of my design the cylinder can be formed with a diameter of 1 inches and operated from a line pressure of p. s. i. to meet the requirements or most any spot-welding operation. A series or welding heads of my design can therefore be mounted side by side on a multiple head machine to produce a two-inch spacing between welds, thus eliminating the necessity for using a source of power other than air on a machine requiring a close spot-weld pattern.

Another advantage or my design resides in the provision of the bushing 2'1 and the extension 39 or non-circular cross section on which the electrode 3 2 is secured. The non-circular cross section of extension til prevents rotation of the piston rod and therefore aids in maintaining the exact location or the working tip oi the electrode M. In addition, it will be noted that no seal contacts any surface that has been exposed to weld spatter. The fit between extension 36 and bu hing; 27 is preferably a close it but not an air-tight fit. The bushing 2'. prevents any weld spatter iroirl accumulating in the bore 26 of sleeve 2; and also serves to wipe the surface oi extension so as to prevent foreign substances from reaching the working surface of piston M.

Although the invention has been described in conjunction with a head for a welder, it will be appreciated that the invention is applicable to various types of fixtures, such as for clamping, etc.

I claim:

1. In combination, a cylinder having a bore, said bore having an enlarged portion extending to one end of cylinder connected with the other portion of the bore by an annular, inwardly off et shoulder, a sleeve in said enlarged bore having one end abutting said shoulder and forming a transverse wall in said cylinder which divides the cylinder into two compartments, said sleeve being shorter in length than said enlarged bore, bushing in said enlarged bore abutting the other end of said sleeve, means securing said bushing; on said cylinder, a piston in each of chambers, and rod extending through said partition wall connecting said pistons together for movement in unison.

2. The comhiraticn iorth claim 1 including inlet ports one of said chambers on opposite sides of the piston therein, and inlet means in the other chamber on only that side of the piston therein which is disposed adjacent the piston in the first mentioned chamber.

3. The combination. forth in claim 1 wherein said piston wi' sleeve provided with an axial exte on which projects outwar ly of the cylinder through said bushing, said extension having means at the outer end thereof for supporting a worlr element.

FRALK. FREDRICK FOLlt-IER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 747,772 Riclcrnan Dec. 22, 1903 2,655,815 Dewey Sept. 29, 1936 2,434,351 Courtelnanche Jan. 13, 1948 2360,1963 Simpson Jan. '25, 1949 2,{l67,628 ONeill Apr. 19, 1949 2,505,771 Hoar et a1. May 2, 1950 

